1. Field of the Invention
The present invention relates to apparatus for storing data and supplying stored data.
2. Description of the Related Art
Data storage units are known that are configured for mass data storage or as RAID (redundant array of inexpensive disks) systems. Such storage units comprise of several disk drives and one or more control units for controlling data input to, and output from, the disk drives. The storage units may be located within a standard size rack unit, typically occupying 1 U to 6 U (1 to 6 rack units) of rack space, and may share the rack with other equipment, and possibly other such data storage units.
Occasionally it is necessary to access the disk drives, for example, for the purposes of replacement of a defective drive, or a drive needing to be upgraded. In some data storage units, access to the disk drives is made possible by the removal of a panel that forms part of the outer main housing of the storage unit.
In recent times it has become known to have a data storage unit in which the disk drives are arranged in several groups, each group supported on a separate support structure that provides electrical connections between the disks drives and a cable connected to the control unit. Each support structure may be slid forward from out of the outer main housing of the storage unit, while the support structure remains electrically connected by the cable to the control unit.
A first problem with such a data storage unit relates to a fan that is arranged to provide a flow of cooling air over the disk drives. During normal operation of the unit, the airflow from the fan is constrained by the outer main housing of the unit, such that it must flow over the disk drives. However, if one of the support structures is withdrawn from the outer main housing, for example to replace a defective disk drive, the airflow is no longer constrained and cooling of the disk drives becomes less effective.
A further problem with known data storage units that has been identified by the Applicant, relates to a lack of flexibility in the arrangement of disk drives within a data storage unit. For example, if a data storage unit having a particular number of disk drives of a particular type is being used, then the options for upgrading the storage capacity and/or performance of the unit are limited.
This latter problem is emphasised by a potential owner of a data storage unit purchasing a unit on his/her current requirements, current technology available, and current budget available. Consequently, a unit may be purchased that soon becomes inadequate and requires replacing.